An optically compensating layer with controlled principal refraction indices (nx, ny, nz) in two in-plane directions and in a thickness direction is required for obtaining a liquid crystal display that compensates birefringence of a liquid crystal cell and provides an excellent omnidirectional display. It should be noted particularly that a VA (Vertically Aligned) type or an OCB (Optically Compensated Bend) type liquid crystal display requires an optically compensating layer providing principal refraction indices in three directions of nx≧ny>nz.
Conventionally, as an optically compensating layer, an optically compensating layer having a single layer structure prepared by stretching a polymer film transversely or biaxially with a tenter has been used (see JP 3(1991)-24502 A, for example). However, such an optically compensating layer with a single layer structure has a problem in that it is not possible to achieve desired retardation values because the difference between the refractive index in the thickness direction and the refractive index in each of the in-plane directions is small.
On the other hand, in order to achieve desired retardation values, an optically compensating layer prepared by laminating at least two stretched polymer films also has been used. For example, there has been known an optically compensating layer prepared by providing two uniaxially stretched polymer films and laminating them so that the directions of the in-plane slow axes of the respective polymer films cross at right angles (see JP 3(1991)-33719 A, for example).
However, since a stretched polymer film is as thick as about 1 mm, an optically compensating layer formed by laminating two or more stretched polymer films will become very thick, thus arising a problem in that the whole thickness of the liquid crystal display including such an optically compensating layer increases.